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542 BOTANICAL GAZETTE [December 

Lichen growth. — As the results of experiments and observations extending 
over a period of 8 years, Fink^ has determined the rate of growth in certain 
crustose and foliose lichens, as determined by measurements of the diameter 
of the thallus, to vary from increases of o . 36 cm. per year for Umbilicaria pus- 
tulata, and 0.42 cm. for Physica pulverulenta, to 1 .3 cm. per year for Parmelia 
Borreri and P. caper ata, and 1.75 cm. for Peltigera canina. Some of the inter- 
mediate annual increments were 0.2-0.75 cm. for Graphis scripta, 0.6 cm. for 
Verrucaria muralis, and 1 . 16 cm. for Parmelia conspersa. In these measure- 
ments Fine has given us practically the only definite data we possess relative 
to the increase in size of these pioneer plants. With regard to migration, Fink 
declines to indulge in speculations regarding possible methods, and says 
" nothing is definitely known further than seeing parts of Cladonia thalli lying 
on some of the quadrats in early stages of ecesis." — Geo. D. Fuller. 

Vegetation studies in Natal. — Bews continues his interesting studies of 
the vegetation of Natal, 14 his latest paper dealing with the ecology of the 
Drakensberg. 15 These mountains exhibit picturesque and even stupendous 
scenery, the highest peaks being more than 11,000 ft. above the sea. The 
most extensive formation, as elsewhere in Natal, is the veld or grassland. The 
alpine veld is composed more of tussock grasses than is the lowland veld, and 
the growth forms are more xerophytic. An interesting formation is the Protea 
veld, dominated by various species of small trees of the genus Protea. The 
climax formation is the bush, dominated by species of Podocarpus, and occupy- 
ing the more protected situations. The mountain top vegetation is markedly 
xerophytic, and is dominated by composites (as Eelichrysum) and heathers 
(as Erica). The last section of the paper deals with successions and inter- 
relations. — H. C. Cowles. 

Tree growth in Iowa. — In presenting data upon tree growth in the vicinity 
of Grinnell, Iowa, Conard 16 brings out several interesting facts in addition to 
the average annual increment of several species. There seems to be conclusive 
evidence that trees are encroaching upon the grasslands, and this is ascribed to 
the elimination of prairie fires during the past half century. While this 
accounts for the present increase of forested areas, it is not regarded as explain- 
ing the presence of grasslands which constituted the natural vegetation upon 
the best soils in the region. These richer soils are very favorable to tree 
growth and the increments are sufficiently large to indicate that timber would 



« Fink, Bruce, The rate of growth and ecesis in lichens. Mycologia 9:138-158. 
IQI7- 

i4 Bot. Gaz. 64:85-86. 19 1 7. 

« Bews, J. W., The plant ecology of the Drakensberg Range. Annals Natal 
Museum 3:5 II_ S65- pis. 4- figs- 3- : 9i7- 

16 Conard, H. S., Tree growth in the vicinity of Grinnell, Iowa. Jour. Forestry 
16:100-106. 1918.